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161.
Ke Y Su B Song X Lu D Chen L Li H Qi C Marzuki S Deka R Underhill P Xiao C Shriver M Lell J Wallace D Wells RS Seielstad M Oefner P Zhu D Jin J Huang W Chakraborty R Chen Z Jin L 《Science (New York, N.Y.)》2001,292(5519):1151-1153
To test the hypotheses of modern human origin in East Asia, we sampled 12,127 male individuals from 163 populations and typed for three Y chromosome biallelic markers (YAP, M89, and M130). All the individuals carried a mutation at one of the three sites. These three mutations (YAP+, M89T, and M130T) coalesce to another mutation (M168T), which originated in Africa about 35,000 to 89,000 years ago. Therefore, the data do not support even a minimal in situ hominid contribution in the origin of anatomically modern humans in East Asia. 相似文献
162.
Pathogenic Antigenic and Molecular Characterization of the Very Virulent Strain(Gx) of Infectious Bursal Disease Virus Isolated in China 总被引:3,自引:0,他引:3
WANG Xiao-mei FU Chao-yang GAO Hong-lei SONG Xiou-long ZENG Xiang-wei ZHANG Man-fu Wallace B L lim 《中国农业科学(英文版)》2003,2(5)
The very virulent infectious bursal disease virus (vvIBDV) strain Gx was isolated from a poutl-try farm in Guangxi Province, China, during 1996. The mortality in the infected flock was 80% and occurred5 days after immunization with serotype I IBD vaccine. The results of antigen-capture ELISA (AC-ELISA),pathogenicity testing, cloning and sequence analysis of the VP2 gene showed that the deduced amino acid se-quence of strain Gx VP2 was the same as vvIBDV UK661, which is considered as a reference strain for Europe-an vvIBDVs. The antigenicity of the Gx strain was the same as an European vvIBDV strain 849. The EID50 of Gx virus was 10-8. 25/0. 2 ml, and the mortality was 64 % when 4 week-old SPF chickens were challenged atdosage of 2 × 103 EID50. We have demonstrated that the IBDV strain Gx isolated in China is vvlBDV according to European standards. 相似文献
163.
Meteorological aspects of the el nino/southern oscillation 总被引:3,自引:0,他引:3
The single most prominent signal in year-to-year climate variability is the Southern Oscillation, which is associated with fluctuations in atmospheric pressure at sea level in the tropics, monsoon rainfall, and wintertime circulation over North America and other parts of the extratropics. Although meteorologists have known about the Southern Oscillation for more than a half-century, its relation to the oceanic El Ni?o phenomenon was not recognized until the late 1960's, and a theoretical understanding of these relations has begun to emerge only during the past few years. The past 18 months have been characterized by what is probably the most pronounced and certainly the best-documented El Ni?o/Southern Oscillation episode of the past century. In this review meteorological aspects of the time history of the 1982-1983 episode are described and compared with a composite based on six previous events between 1950 and 1975, and the impact of these new observations on theoretical interpretations of the event is discussed. 相似文献
164.
The presence or absence of a change in the ambient stimulus conditions upon entry into a food source controlled the frequency with which pigeons choose one of two concurrently available grain sources. Such changes characteristically accompany the production of response-produced food and account for prior reports of responding to produce food in the presence of freely available food. 相似文献
165.
A Lyman-alpha airglow of atomic hydrogen measured in the outer atmosphere of Venus showed that atomic hydrogen is present. The variation as a function of height indicates that the temperature of the upper atmosphere of Venus is lower than that of Earth. An ultraviolet airglow of atomic oxygen was not found. An ultraviolet nightglow was observed on the dark limb. 相似文献
166.
Advanced technology paths to global climate stability: energy for a greenhouse planet 总被引:6,自引:0,他引:6
Hoffert MI Caldeira K Benford G Criswell DR Green C Herzog H Jain AK Kheshgi HS Lackner KS Lewis JS Lightfoot HD Manheimer W Mankins JC Mauel ME Perkins LJ Schlesinger ME Volk T Wigley TM 《Science (New York, N.Y.)》2002,298(5595):981-987
Stabilizing the carbon dioxide-induced component of climate change is an energy problem. Establishment of a course toward such stabilization will require the development within the coming decades of primary energy sources that do not emit carbon dioxide to the atmosphere, in addition to efforts to reduce end-use energy demand. Mid-century primary power requirements that are free of carbon dioxide emissions could be several times what we now derive from fossil fuels (approximately 10(13) watts), even with improvements in energy efficiency. Here we survey possible future energy sources, evaluated for their capability to supply massive amounts of carbon emission-free energy and for their potential for large-scale commercialization. Possible candidates for primary energy sources include terrestrial solar and wind energy, solar power satellites, biomass, nuclear fission, nuclear fusion, fission-fusion hybrids, and fossil fuels from which carbon has been sequestered. Non-primary power technologies that could contribute to climate stabilization include efficiency improvements, hydrogen production, storage and transport, superconducting global electric grids, and geoengineering. All of these approaches currently have severe deficiencies that limit their ability to stabilize global climate. We conclude that a broad range of intensive research and development is urgently needed to produce technological options that can allow both climate stabilization and economic development. 相似文献
167.
Wallace SJ 《Science (New York, N.Y.)》1881,2(48):232-233
168.
Foroughi J Spinks GM Wallace GG Oh J Kozlov ME Fang S Mirfakhrai T Madden JD Shin MK Kim SJ Baughman RH 《Science (New York, N.Y.)》2011,334(6055):494-497
Rotary motors of conventional design can be rather complex and are therefore difficult to miniaturize; previous carbon nanotube artificial muscles provide contraction and bending, but not rotation. We show that an electrolyte-filled twist-spun carbon nanotube yarn, much thinner than a human hair, functions as a torsional artificial muscle in a simple three-electrode electrochemical system, providing a reversible 15,000° rotation and 590 revolutions per minute. A hydrostatic actuation mechanism, as seen in muscular hydrostats in nature, explains the simultaneous occurrence of lengthwise contraction and torsional rotation during the yarn volume increase caused by electrochemical double-layer charge injection. The use of a torsional yarn muscle as a mixer for a fluidic chip is demonstrated. 相似文献
169.
170.